In a transmission type image display apparatus such as a liquid crystal display apparatus, a direct type planar light source apparatus may be used as a back light unit. Recently, a direct type planar light source apparatus having a plurality of light emitting elements as a light source has been used.
For example, the direct type planar light source apparatus includes a substrate, light emitting elements, light flux controlling members (expanding lenses), and a light diffusion member (diffuser plate). The light emitting elements are arranged on the substrate in a matrix pattern. The light flux controlling members are arranged on the respective light emitting elements. The light flux controlling members spread light emitted from the respective light emitting elements in a plane direction of the substrate. Light emitted from the light flux controlling members is diffused by the light diffusion member to illuminate an illumination target member (for example, a liquid crystal panel) in a plane shape.
When the light flux controlling members are positioned on the substrate, positioning bosses (convex parts) may be formed in the bottoms of the light flux controlling members to insert these bosses into holes formed on the substrate (for example, refer to Patent Literature (hereinafter, abbreviated as PTL) 1).
PTL 1 discloses a lens body including lenses and support parts for positioning the lenses on a substrate. Columnar convex parts (bosses) are formed on a contact surface (a surface in contact with the substrate) of the support parts, and through holes corresponding to the convex parts are formed on the substrate. By inserting the convex parts of the support parts of the lens body into the through holes formed on the substrate, the lens body (plurality of lenses) is positioned on the substrate.